1. Field of the Invention
The present invention relates to an information reproducing apparatus and an information recording apparatus capable of further promoting a recording density by using a reproducing and recording system using near-field light, and to a recording medium, an information reproducing method and an information recording method used in information reproduction or recording utilizing near-field light.
2. Background Information
In recent years, the promotion of a recording density of information reproducing/recording apparatus starting from a hard disk apparatus has lost interest and there is now an interest for a new reproducing and recording system in place of an existing system in order to promote the recording density. At present, as a technology for outstandingly promoting such a recording density, there has been proposed an information reproducing system using near-field light of which has already been reduced into practice in the United States.
Near-field light is provided with a high resolution equal to or higher than the diffraction limit of light and, accordingly, a pit on an information recording medium can be made further smaller than that in a conventional system. Therefore, the recording density can be increased up to several tens G bits/square inch. According to the system, the recording density does not depend on the wavelength of light but on the very small shape or size at a front end of a head.
However, even in the case of the information reproducing/recording apparatus using near-field light, the head is controlled such that the head is not shifted from a row of data marks and accordingly, it is necessary to provide tracking marks on the recording medium. The tracking marks do not hold data and accordingly, there poses a problem in which the data marks are eroded by an amount of the tracking marks, constituting a hazard in high density formation.
Further, by a single data mark, in principle, information other than “0” and “1” cannot be expressed and therefore, there poses a problem in which there is a limit in high density formation by a unit of the data mark.
Hence, the invention has been carried out in view of the above-described and it is an object thereof to provide an information reproducing apparatus and an information recording apparatus capable of further promoting a recording density by using a reproducing and recording system using near-field light as well as a recording medium, an information reproducing method and an information recording method used in information reproduction or recording utilizing near-field light.